A gas turbine engine typically includes a fan section, a compressor section, a combustor section, and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section.
In the pursuit of ever higher efficiencies, gas turbine manufacturers have long relied on high and higher turbine inlet temperatures to provide boosts to overall engine performance. In typical modern gas turbine engine applications, gas path temperatures within the turbine exceed the melting point of the component constituent materials. Due to this, dedicated cooling air must be extracted from the compressor and used to cool gas path components in the turbine. This incurs significant cycle penalties especially when cooling air is utilized in the low pressure turbine (sometimes referred to as the power turbine).
A significant driver of turbine cooling is the spatially varying temperature distribution of the gas path. The nature of the combustion method and geometry produces a variance is gas temperature in both the radial and circumferential directions of flow. This variation in gas temperature also shifts and changes in magnitude and shape as the hot gases progress through the turbine.
To help minimize the amount of cooling air needed for the gas path turbine components, an understanding of the spatially resolved temperature of the gas stream is desired to tailor cooling to areas of high heat load. This understanding is achieved through temperature measurements through the gas path. These are typically achieved through direct measurement on thermocouple probes, such as kiel head probes, protruding into the gas path situated. The thermocouple is typically attached to the leading edge of a static structure or rake and protrudes into the gas path allowing direct measurement of the total gas temperature.
However, since the probe is mounted to a static structure which generally needs to be several hundred degrees cooler than the gas path, film cooling on the static structure is generally needed to cool the static structure. The film cooling, which is typically machined into the static structure, generally directs the cooling air at the thermocouple. This perturbs the flow temperature measurements by the thermocouple and causes large discrepancies in actual values. Therefore, there is a need for improved temperature measurements in the gas path of a gas turbine engine.